1. Field of the Disclosure
The present invention relates generally to an optical image capture system, and more particularly to an illumination assembly for producing a substantially uniform intensity at an image sensor of the image capture system.
2. Description of the Related Art
Image capture systems are used in a variety of applications. Such systems may be combined in an all-in-one unit that includes image capture, image formation, and facsimile functions. Image capture systems may also be independent and only capable of performing an image capture function. Digital photograph technology has progressed with imaging units now able to produce high quality two dimensional images in a single step process. The imaging units are also economical allowing them to be utilized in new applications, such as document scanning technology.
Conventional image capture systems utilizing digital photograph technology include a light source that illuminates a document plane and an image sensor that captures an image of the document plane. In order to obtain a high quality scan, substantially uniform illumination is desired. One existing approach has been to include one or more correction devices that correct any non-uniformity effects that occur between the light source and the document plane to provide substantially uniform illumination at the document plane. However, it has been observed that additional non-uniformity effects may occur between the document plane and the image sensor. These additional non-uniformities can cause degradation of the image captured by the image sensor even where uniform illumination of the document plane is achieved.
Specifically, some image sensors used with digital photograph technology possess an inherent intensity roll-off from the center of the document outward thereby causing a lower perceived intensity at the edges of the document. Some lens configurations can add to this roll-off. As a result, a uniformly illuminated document plane appears slightly to non-uniform in the resulting image capture. Further, in some image capture systems, one or more mirrors may be desired between the document plane and the image sensor in order to reduce the overall footprint of the system. However, variation between the reflectance of the mirror and the incident angle of the light over the surface of the mirror can create additional non-uniformities. Specifically, areas of the document plane having a larger incident light angle in relation to the mirror normal experience a significantly different illumination intensity in comparison with areas having a smaller incident light angle.
Accordingly, it will be appreciated that an image capture system that corrects the non-uniformity effects that occur between the document plane and the image sensor to achieve substantially uniform illumination at the image sensor is desired.